BROCADE IP PRIMER

The Routing TableLet's take a moment to go over what we're looking at.• Start Index. Each routing table entry is numbered. The “start index” tellsus what number it will start with. In this case, its 1. There are two routesin this table. Each route is labeled with a number: “1” and “2.”• Destination. This is the network that an incoming packet is heading for.When a router receives the incoming packet, it will check the destinationaddress in the IP header. Then, it will check its routing table to see if itknows how to get to where the packet wants to go. If it can, it forwards thepacket on its way. If it can't, the packet is dropped, and the senderreceives an ICMP message.• NetMask. This is the subnet mask of the destination network. It's importantwhen you look at the routing table to remember to pair theDestination with the NetMask. There will be times when it appears thatthere are multiple identical entries in the routing table, but closer inspectionwill show that there are actually two entries with the sameDestination, but different NetMasks.• Gateway. This is the IP address of the router that the incoming packetshould be forwarded to. If the router is directly connected to the Destinationsubnet, the gateway is listed as 0.0.0.0.• Port. This is the interface that is either connected to the Destination subnet,or is connected to the gateway of the Destination subnet.• Cost. This is the Administrative Distance of the route. We'll talk moreabout this one later.• Type. This explains how the route got in the routing table in the firstplace. Some types you may see will include:— B - the route was learned through BGP— D - the route is directly connected to this switch— R - the route was learned through RIP— S - the route is statically configured on the switch— O - the route was learned through OSPF— * - the route is a candidate default routeConnected RoutesHow did these routes get into Switch A's routing table? Remember Chapter 2?We configured a static IP address on two of the interfaces. On any Layer 3-capable device (including workstations), when you configure one of your interfaceswith a static IP address, an entry is automatically made in the device'srouting table. When you configure the IP address, you are saying that thisdevice is a participating member of this particular subnet.Brocade IP Primer 221